1. Field of the Invention
The present invention relates to an apparatus for improving rise characteristics of a direct current power supply source in order to supply a load with a direct current having efficient rise characteristics, even when a direct current power supply having "Walk-in" characteristics, wherein a capacity for supplying power gradually increases after starting and reaches a rated value after more than several seconds, is used.
2. Description of the Related Art
In equipment such as communication facilities, power is fed in the form of a direct current to each unit. The direct current is usually obtained by rectifying an alternating current such as commercial power, with a rectifier.
Among such kinds of rectifiers, there is one that cannot supply maximum rated power immediately after starting but reaches the rated power after several to several tens of seconds have elapsed. The reason why the rectifier is given such a characteristic is that a generator generating an alternating current fed to the rectifier is in danger of stalling if the generator is over-loaded immediately after starting, and thus, that danger must be avoided. This characteristic of rectifiers is called a "Walk-in" characteristic.
On the other hand, on a load side, though various load states are supposed, in a general case, the load is often an electronic circuit including a power supply board. In the case of the power supply board as an example, a circuit construction including a dc-dc converter is widely employed in general power supply boards. A power supply board having a circuit construction including a dc-dc converter usually has rise characteristics such that circuits do not operate while an input current is below a certain threshold value, and normally operate if the input current is above the threshold value.
If the dc-dc converter having such rise characteristics is directly connected to the aforesaid rectifier, an output current of the rectifier violently fluctuates as discussed later. In the case of communication facilities, the violent fluctuation of the output current of the rectifier causes communication errors or generation of alarm transmission, or in a worst case, causes a breakdown of the facilities.